CDKN2 in HPV-positive and HPV-negative cervical-carcinoma cell lines

Human cervical cancers frequently contain retinoblastoma protein (Rb) that is inactivated by binding with human papilloma virus (HPV) E7 protein or through mutation. The CDKN2 gene encodes p 16^INK4 which inhibits cdk4-cyclin D phosphorylation of Rb, preventing the G₁-S transition. To determine whether abnormalities of CDKN2 occur in cervical-cancer cells, 11 cervical cell lines, including 8 HPV-positive cell lines, 2 HPV-negative cell lines containing mutant Rb, and one tumorigenic cell line derived from normal cervical cells following transfection with HPV-16 and v-H-ras (CX16-2HR), were analyzed. No cell line had a homozygous deletion of exon 1 or 2 of CDKN2, and only one cell line, CX16-2HR, had an altered DNA sequence, which represents a common polymorphism at codon 148. To exclude the possibility of other subtle inactivating mutations, immunoblot analysis of protein lysates was performed using a polyclonal anti-p 16^INK4 rabbit anti-serum. Abundant levels of normal-sized pl6^INK4 were observed in all cell samples. Thus, no alterations of CDKN2 were detected in these cervical cell lines. These results confirm that mutational inactivation of p 16^INK4 is a rare event in tumor samples with compromised Rb activity.